T i m wrote in message +ADw-4u2d301qj5k31tmigh82e9csjpk11asqij+AEA-4ax.com+AD4-...
+-ACY-gt+-ADs-Hi all,+-ADw-BR+-AD4- +-ACY-gt+-ADsAPA-BR+-AD4- +-ACY-gt+-ADs-Following
the recent thread re 90 deg drills and grinder conversions+-ADw-BR+-AD4-
+-ACY-gt+-ADs-.. I bought a 13m capacity key'd chuck with
1/2+-ACY-quot+-ADs- -20 UNF female thread+-ADw-BR+-AD4- +-ACY-gt+-ADs-(with SDS
adaptor) from the market today (for +-AKM-3) to play with +-ADs--)+-ADw-BR+-AD4-
+-ACY-gt+-ADsAPA-BR+-AD4- +-ACY-gt+-ADs-Mum and Dad happened in Makro and
collected the nutool mains drill and+-ADw-BR+-AD4- +-ACY-gt+-ADs-mini grinder
combo for +-AKM-14.99 (+--Vat) for me (bless) +-ADs--)+-ADw-BR+-AD4-
+-ACY-gt+-ADsAPA-BR+-AD4- +-ACY-gt+-ADs-So, to make my 90 deg drill
+-ACY-lt+-ADs-the theory is+-ACY-gt+-ADs- I might be able to drill /+-ADw-BR+-AD4-
+-ACY-gt+-ADs-bore (on the lathe) and tap the chuck out to 14mm then it would
screw+-ADw-BR+-AD4- +-ACY-gt+-ADs-directly onto the angle driver removing the
need for the 'converter'+-ADw-BR+-AD4- +-ACY-gt+-ADs-in-between? In this config
the 'length' of the whole unit will be+-ADw-BR+-AD4- +-ACY-gt+-ADs-about
6+-ACY-quot+-ADs- (150mm).+-ADw-BR+-AD4- +-ACY-gt+-ADsAPA-BR+-AD4- +-ACY-gt+-ADs-So,
from what I can see, the tapping drill for 1/2+-ACY-quot+-ADs- UNF is 10.8mm
with+-ADw-BR+-AD4- +-ACY-gt+-ADs-the outer thread size of about 12.4 mm. I think
the tapping drill size+-ADw-BR+-AD4- +-ACY-gt+-ADs-for a '14' mm thread is 12mm
with a final thread size of about 13.7mm?+-ADw-BR+-AD4- +-ACY-gt+-ADs-Assuming
I'm right with the numbers do you think I could get away with+-ADw-BR+-AD4-
+-ACY-gt+-ADs-that?+-ADw-BR+-AD4- +-ACY-gt+-ADsAPA-BR+-AD4- +-ACY-gt+-ADs-All the
best ..+-ADw-BR+-AD4- +-ACY-gt+-ADsAPA-BR+-AD4- +-ACY-gt+-ADs-T i m+-ADw-BR+-AD4-
Perfectly feasible if done with care
Keeping everything concentric will be important.
CHuck a piece of scrap 3/4+ACI- or similar steel bar in the three jaw, turn down
to 1/2+ACI- and fit the drill chuck onto this and tighten using all three key
holes in turn and tighten some more+ACE- yuo do not want this moving later+ACE-
Bore out the back of the drill chuck then screw cut most of the material
for the 14mm thread. If your lathe is imperial, get the nearest you can with
change wheels and gearbox but don't disengage the clasp nuts between passes.
Instead stop the motor and wind back by hand/under power otherwise you will
not be able to pick up the cut.
Depending on how close you can get to the correct pitch, stop before the
whole thread is cut and finish off with a plug tap.
The reason for the screw cutting is simple that there is quite a lot of meat
to remove on a 14mm thread and hand tapping a blind hole this size will be
quite hard work and risks the work slipping and loss of concentricity.
run out in a drill at angle grinder speeds will be bad news if not downright
You might want to find a way of putting a couple of spanner flats on the
chuck body (not the tightening ring) so you can get it off the angle grinder
as it will tighten in use. Greasing the thread will help too.